Here's the dope: Boris Johnson, who regularly bikes to and from the office, was Just Riding Along when he heard a cry for help from Franny Armstrong. Some teenagers were threatening Armstrong with an iron pipe. Johnson chased the girls away, then escorted Ms Armstrong the rest of the way home.

Boris Johnson is a pretty big dude. Armstrong admits that she had voted for rival Ken Livingstone in the 2008 mayoral election. But Ms Armstrong added: "If you find yourself down a dark alleyway and in trouble I think Boris would be of more use than Ken."